Continued building the main avionics rack behind the panel. The main structure is now mostly complete, so today I drilled and countersunk most of the rest of the nutplate holes. Primed most parts. Clamped the base plate and supports into the airplane to see what the best way to attach it would be. It turns out the flange of the forward cross-brace sits at a slightly different angle from the z-channel just forward of it. This means that the baseplate does not sit flat (see photo #2). I began to figure out how I'll correct for this. My first thought was to bend the three supports a few degrees, but they are made of 0.090" aluminum, and my bending brake is only capable of handling 0,040". Next, I considered bending the baseplate just aft of the support angle, but this would mis-align several of the threaded standoffs between the lower and upper levels. Finally, I researched screw shims and tapered washers at McMaster-Carr. I found a few items that might work, so I ordered them. We'll see.